Fix: rem2pi for negative values greater than 2pi (#36233)

* Fix rem2pi for RoundToZero

* add extra tests for rem2pi

Author: mgautam98

base/math.jl

@@ -1001,7 +1001,7 @@ function rem2pi(x::Float64, ::RoundingMode{:ToZero})
     ax = abs(x)
     ax <= 2*Float64(pi,RoundDown) && return x
 
-    n,y = rem_pio2_kernel(x)
+    n,y = rem_pio2_kernel(ax)
 
     if iseven(n)
         if n & 2 == 2 # n % 4 == 2: add pi

test/numbers.jl

@@ -2507,6 +2507,14 @@ end
     @test rem2pi(T(-4), RoundNearest) ≈ 2pi-4
     @test rem2pi(T(-4), RoundDown)    ≈ 2pi-4
     @test rem2pi(T(-4), RoundUp)      == -4
+    @test rem2pi(T(8), RoundToZero)  ≈ 8-2pi
+    @test rem2pi(T(8), RoundNearest) ≈ 8-2pi
+    @test rem2pi(T(8), RoundDown)    ≈ 8-2pi
+    @test rem2pi(T(8), RoundUp)      ≈ 8-4pi
+    @test rem2pi(T(-8), RoundToZero)  ≈ -8+2pi
+    @test rem2pi(T(-8), RoundNearest) ≈ -8+2pi
+    @test rem2pi(T(-8), RoundDown)    ≈ -8+4pi
+    @test rem2pi(T(-8), RoundUp)      ≈ -8+2pi
 end
 
 import Base.^